it's labelled as number of removals, I think it's an absolute number of removed posts per day(?)

edit: sibling comment points out it's per 12 hour period, not per day

edit: as for the cap of 50 - it seems that is the number of posts shown on a first page of r/all (using old reddit), so it seems that means that all 50 slots "should" be filled with posts that have been removed